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Abdominal Aortic Aneurysm
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Abdominal Aortic Aneurysm
, Aortic Aneurysm of Abdominal Aorta, Abdominal Aortic Ectasia
See Also
Abdominal Pain in Older Adults
Definitions
Abdominal Aortic Aneurysm
Abdominal aorta diameter 3.0 cm or greater
Abdominal Aortic Ectasia
Abdominal aorta diameter 2.5 to 2.9 cm
Epidemiology
Ruptured AAA results in 11,000 deaths per year
Responsible for 4-5% of sudden deaths in the United States
Age Distribution
Age under 50 years old
Uncommon
Age over 60 years
Incidence
5-7% of over 60 years old
Accounts for 75% of aneurysms
Age 65 to 74 years old
Tenth leading cause of death
Ages 74-84 years old
Men: 12.5%
Incidence
of AAA
Women: 5.2%
Incidence
of AAA
Male:Female Ratio
Age: 60-64 year old: 11:1
Age: 85-90 year old: 3:1
Ethnicity
Black and hispanic patients are at lower risk of AAA
Pathophysiology
Elastin and collagen degradation in aorta wall
Provoked by environmental stressors
Inflammation (esp.
Tobacco Abuse
)
Possible association with
Chlamydia pneumoniae
Increased wall tension (e.g.
Hypertension
, PVD)
Risk Factors
AAA Development
Similar to other
Cardiovascular Risk Factor
s
Tobacco Abuse
(90% of patients have used
Tobacco
)
First degree relative has up to a 19% risk of AAA
Coronary Artery Disease
(including prior
Myocardial Infarction
)
Peripheral Arterial Disease
Hypertension
Age over 65 years old
Male gender
Risk Factors
AAA Rupture
Female gender
Tobacco Abuse
Obstructive Lung Disease
(FEV1 decreased)
Hypertension
Causes
Associated with Atherosclerosis in only 25% of patients
Aortic Dissection
Mycotic Infection
Cyst
ic Medial Necrosis
Ehlers-Danlos Syndrome
Presentation
Asymptomatic in 75% of AAA
Abrupt onset severe pain unrelieved by position change
Classic: Back pain or
Abdominal Pain
, pulsatile mass and
Hypotension
Suggestive of aneurysm enlargement or rupture
Classic triad only present in 25-50% of cases
Cryptic presentations are common
Misdiagnosis as
Diverticulitis
,
GI Bleed
, Musculoskeletal cause is common (60% initial misdiagnosis rate)
May present as referred pain to a wide range of regions (to chest, back and
Scrotum
)
Microscopic Hematuria
(and rarely
Gross Hematuria
) may lead to misdiagnosis of
Renal Colic
Aortic Rupture
(20% present ruptured)
Free Intraperitoneal Rupture (Catastrophic)
Acute abdominal or back pain
Flank
Ecchymosis
Cardiovascular Collapse (
Hypotension
)
Sudden Death
Sentinal Bleed (small posterolateral wall tear)
Acute pain (constant)
Syncope
Pulsatile abdominal mass
Hemodynamically stable with
Tachycardia
Needs Emergent Intervention before full rupture
Symptoms
Pain in
Abdomen
, Flank or Back
Early satiety
Nausea
and
Vomiting
Signs
Pulsatile abdominal mass
Technique
Mass occurs left of midline at level of
Umbilicus
Position patient supine, knees flexed, while exhaling
May be associated with abdominal bruit
Efficacy of palpation for pulsatile mass >3 cm
Test Sensitivity
: 68%
Test Specificity
: 75%
Fink (2000) Arch Intern Med 160(6):833-6 [PubMed]
Larger AAA has higher likelihood of palpation
AAA 3-4 cm palpable in 29% of cases
AAA 5 cm palpable in 76% of cases
Lederle (1999) JAMA 281:77-82 [PubMed]
Signs
Peripheral pulses
Check pulse
Femoral artery
Popliteal artery
Interpretation
Bounding Pulse
suggests possible AAA
Peripheral artery aneurysmal swelling
Femoral aneurysm predicts AAA in 85% of cases
Popliteal aneurysm predicts AAA in 62% of cases
Signs
Miscellaneous
Cullen's Sign
Periumbilical
Bruising
Grey Turner's Sign
Flank
Bruising
(retroperitoneal hematoma)
Differential Diagnosis
See Acute
Acute Abdominal Pain
See
Abdominal Pain in Older Adults
See
Acute Abdominal Pain Causes
Acute Cholecystitis
Perpforated peptic ulcer
Diverticulitis
Nephrolithiasis
Diagnosis
AAA is most commonly identified as an
Incidental Imaging Finding
Normal abdominal aorta diameter
Male: 17-21 mm (infrarenal)
Female: 15-19 mm (infrarenal)
Abnormal Localized aortic dilatation
Aortic diameter exceeds 1.5 times normal size
Aortic diameter exceeds 30 mm
Imaging
Gene
ral
See
Ultrasound in Abdominal Aortic Aneurysm
See
CT in Abdominal Aortic Aneurysm
Incidental Findings on Abdominal XRay (low
Specificity
)
Calcified AAA wall visible in only 67-75%
Soft tissue mass
Loss of psoas shadow
Loss of renal outline
Imaging
Screening for Abdominal Aortic Aneurysm
Indications for one-time routine screening
USPTF Guidelines (2014)
Gene
ral screening above age 75 years is not typically recommended due to likelihood of comorbidity
Men 65 to 75 years old
History of
Tobacco Abuse
(>100
Cigarette
s lifetime, Level B recommendation)
Other AAA Risk Factor (see risk factors above, Level C recommendation)
Women 65 to 75 years old
History of
Tobacco Abuse
(inconclusive, consider screening)
Society for Vascular Medicine Guidelines
Men age 60 to 85 years
Women age 60 to 85 years with
Cardiac Risk Factor
s
Men and Women age >50 years and history of AAA in first degree relative
First choice imaging study
See
Ultrasound in Abdominal Aortic Aneurysm
Alternative for
Obesity
or excess intestinal gas
Standard CT (see
CT in Abdominal Aortic Aneurysm
)
Imaging
Monitoring protocol for Abdominal Aortic Aneurysm
Ultrasound in Abdominal Aortic Aneurysm
Aorta diameter <3.0 cm
No surveillance (although some consider rescreening if 2.5 to 2.9 cm)
Aorta diameter 3.0 to 3.9 cm
Repeat
Ultrasound of AAA
every 2 to 3 years
Typical rate of expansion: 1-4 mm/year
Aorta diameter 4.0 to 5.4 cm
Repeat
Ultrasound of AAA
(or
CT in Abdominal Aortic Aneurysm
) every 6-12 months
Consider Surgical
Consultation
for AAA 5.0 cm or greater (or faster rate of expansion)
Typical rate of expansion: 3-5 mm/year
Aorta diameter >5.4 cm
Surgical
Consultation
for elective AAA repair
Typical rate of expansion: 7-8 mm/year (for AAA >6.0 cm)
CT in Abdominal Aortic Aneurysm
Indications
Surgeon will order on referral
See surgery indications below
Ultrasound
aorta >5.4 cm
Change >0.5 cm in 6 months or >1 cm in 1 year
Interpretation
Repeat
Ultrasound
q3 months if aorta <5.5 cm
Vascular surgery consult for indications below
Admit patients with aorta >8 cm on
CT Abdomen
Imaging
Preoperative evaluation
First Choice
CT Angiogram
Alternative in specific circumstances
Abdominal Aortography
MRI with MRA in abdominal aortic aneurysm
Precautions
Delayed diagnosis of AAA related symptoms has a very high mortality
Have a low threshold for bedside
Abdominal Aorta Ultrasound
in age >50-60 years with
Abdominal Pain
or back pain
Management
Surgical Repair
Indications: Symptomatic Aneurysm
Symptoms: Abdominal, back or
Groin Pain
with AAA
Concurrent
Hypotension
suggests ruptured AAA
Urgent surgical repair (high risk of rupture)
Indications: Asymptomatic Aneurysm
Aortic aneurysm diameter >5.4 cm
AAA diameter 4-5 cm and
Enlarging 0.5 cm in 6 months or
Enlarging 1 cm in 1 year
AAA diameter 7 cm with significant comorbidity
Left Ventricular Dysfunction
(CHF)
Severe
Chronic Obstructive Pulmonary Disease
Noncorrectable symptomatic
Coronary Artery Disease
Operative Risk
Myocardial Infarction
(4.7% mortality)
Mortality
Elective repair: 3-5% (similar risk )
Symptomatic Aneurysm: 26%
Ruptured Aneurysm: 35-40%
Sullivan (1990) J Vasc Surg 11:799-803 [PubMed]
Operative techniques
Open AAA repair (traditional)
Higher 30 day mortality (4-5%) than endovascular repair (1-2%)
However, endovascular repair benefit is absent by 1-2 years following repair
Greenhalgh (2010) N Engl J Med 362(20): 1863-71 [PubMed]
Endovascular repair has a higher rate of later complications
Graft complications
Second procedures required
Endovascular AAA repair (Endograft)
Optimal emergency stabilization procedure if infrarenal AAA (especially in elderly patients)
Also consider if high risk with <2 years
Life Expectancy
Surveillance post procedure
Requires CT at 1, 6 and 12 months after procedure
Annual surveillance required after the first year
Adverse events (10-15%)
Lower 30 day mortality than open AAA repair
Risk of blood leakage around endograft
Also risk of stent graft or migration
Similar 5 year mortality outcomes to open repair
References
(2005) Lancet 365:2179-86 [PubMed]
Preoperative risk reduction
See
Preoperative Cardiovascular Evaluation
Perioperative Beta Blocker
Significantly decreases mortality
Used bisoprolol 5 mg daily >1 week pre-surgery
Goal
Heart Rate
: 60 (keep systolic BP >100)
Poldermans (1999) N Engl J Med 341:1789-94 [PubMed]
Tobacco Cessation
Statin
s for lipid lowering
COPD
optimization
Renal Function
optimization in
Chronic Kidney Disease
Prognosis
Mortality from ruptured aneurysm: 90% (50% do not reach the hospital alive)
Elective AAA Repair: 61% five year survival
Risk of AAA rupture
AAA <5.5 cm: 0.6-3.2% annual risk of AAA rupture
AAA 5.5 - 6 cm: 9% annual risk of AAA rupture
AAA 6 - 6.9 cm: 10% annual risk of AAA rupture (40% lifetime risk of rupture)
AAA 7 cm: 33% annual risk of AAA rupture (50% lifetime risk of rupture)
Course of small aortic aneurysms (<4 cm)
Increase median of 2 mm per year (up to 8 mm/year)
Biancari (2002) Am J Surg 183:53-5 [PubMed]
Comorbid cardiopulmonary disease is common in AAA
Prevention
Slowing progression of AAA
Tobacco Cessation
Tobacco
increases the incremental AAA growth rate by 0.4 mm per year
Sweeting (2012) Br J Surg 99(5): 655-65 [PubMed]
No strong evidence for specific antihypertensives or lipid lowering agents prior to repair
Patient Education
Indication for immediate evaluation in known AAA
Pain in low back, groin, legs or buttocks
References
Weinstock in Herbert (2018) EM:Rap 18(6): 2-3
Brewster (2003) J Vasc Surg 37:1106-17 [PubMed]
Keisler (2015) Am Fam Physician 91(8): 538-43 [PubMed]
Lederle (2003) Ann Intern Med 139:516-23 [PubMed]
Newell (1997) Am Fam Physician 56(4):1103-8 [PubMed]
Santilli (1997) Am Fam Physician 56(4):1081-90 [PubMed]
Upchurch (2006) Am Fam Physician 73(7):1198-206 [PubMed]
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